concordancefit {survival}  R Documentation 
This is the working routine behind the concordance
function. It
is not meant to be called by users, but is available for other packages
to use. Input arguments, for instance, are assumed to all be the
correct length and type, and missing values are not allowed: the calling
routine is responsible for these things.
concordancefit(y, x, strata, weights, ymin = NULL, ymax = NULL,
timewt = c("n", "S", "S/G", "n/G2", "I"), cluster, influence =0,
ranks = FALSE, reverse = FALSE, timefix = TRUE, keepstrata=10,
std.err = TRUE)
y 
the response. It can be numeric, factor, or a Surv object 
x 
the predictor, a numeric vector 
strata 
optional numeric vector that stratifies the data 
weights 
options vector of case weights 
ymin , ymax 
restrict the comparison to response values in this range 
timewt 
the time weighting to be used 
cluster , influence , ranks , reverse , timefix 
see the help for the

keepstrata 
either TRUE, FALSE, or an integer value.
Computations are always done within stratum, then added. If the
total number of strata greater than 
std.err 
compute the standard error; not doing so saves some compute time. 
This function is provided for those who want a “direct” call to the concordance calculations, without using the formula interface. A primary use has been other packages. The routine does minimal checking of its input arguments, under the assumption that this has already been taken care of by the calling routine.
a list containing the results
Terry Therneau